﻿/*
 * DotNetCrypt - an open source library of cryptographic algorithms for .NET
 * Copyright (C) 2009 David Musgrove
 * 
 * This file is part of DotNetCrypt.
 *
 * DotNetCrypt is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * DotNetCrypt is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

using System;

namespace DotNetCrypt
{
// ReSharper disable InconsistentNaming
    /// <summary>
    /// Performs a cryptographic transformation of data using the
    /// <see cref="RC2" /> algorithm. This class cannot be inherited.
    /// </summary>
    public sealed class RC2ManagedTransform : ManagedTransformBase
// ReSharper restore InconsistentNaming
    {
        private byte[] _keyBuffer;
        private ushort[] _keyWords;

        static private readonly byte[] _piTable = {
                                                      0xd9, 0x78, 0xf9, 0xc4, 0x19, 0xdd, 0xb5, 0xed, 0x28, 0xe9, 0xfd, 0x79, 0x4a, 0xa0, 0xd8, 0x9d,
                                                      0xc6, 0x7e, 0x37, 0x83, 0x2b, 0x76, 0x53, 0x8e, 0x62, 0x4c, 0x64, 0x88, 0x44, 0x8b, 0xfb, 0xa2,
                                                      0x17, 0x9a, 0x59, 0xf5, 0x87, 0xb3, 0x4f, 0x13, 0x61, 0x45, 0x6d, 0x8d, 0x09, 0x81, 0x7d, 0x32,
                                                      0xbd, 0x8f, 0x40, 0xeb, 0x86, 0xb7, 0x7b, 0x0b, 0xf0, 0x95, 0x21, 0x22, 0x5c, 0x6b, 0x4e, 0x82,
                                                      0x54, 0xd6, 0x65, 0x93, 0xce, 0x60, 0xb2, 0x1c, 0x73, 0x56, 0xc0, 0x14, 0xa7, 0x8c, 0xf1, 0xdc,
                                                      0x12, 0x75, 0xca, 0x1f, 0x3b, 0xbe, 0xe4, 0xd1, 0x42, 0x3d, 0xd4, 0x30, 0xa3, 0x3c, 0xb6, 0x26,
                                                      0x6f, 0xbf, 0x0e, 0xda, 0x46, 0x69, 0x07, 0x57, 0x27, 0xf2, 0x1d, 0x9b, 0xbc, 0x94, 0x43, 0x03,
                                                      0xf8, 0x11, 0xc7, 0xf6, 0x90, 0xef, 0x3e, 0xe7, 0x06, 0xc3, 0xd5, 0x2f, 0xc8, 0x66, 0x1e, 0xd7,
                                                      0x08, 0xe8, 0xea, 0xde, 0x80, 0x52, 0xee, 0xf7, 0x84, 0xaa, 0x72, 0xac, 0x35, 0x4d, 0x6a, 0x2a,
                                                      0x96, 0x1a, 0xd2, 0x71, 0x5a, 0x15, 0x49, 0x74, 0x4b, 0x9f, 0xd0, 0x5e, 0x04, 0x18, 0xa4, 0xec,
                                                      0xc2, 0xe0, 0x41, 0x6e, 0x0f, 0x51, 0xcb, 0xcc, 0x24, 0x91, 0xaf, 0x50, 0xa1, 0xf4, 0x70, 0x39,
                                                      0x99, 0x7c, 0x3a, 0x85, 0x23, 0xb8, 0xb4, 0x7a, 0xfc, 0x02, 0x36, 0x5b, 0x25, 0x55, 0x97, 0x31,
                                                      0x2d, 0x5d, 0xfa, 0x98, 0xe3, 0x8a, 0x92, 0xae, 0x05, 0xdf, 0x29, 0x10, 0x67, 0x6c, 0xba, 0xc9,
                                                      0xd3, 0x00, 0xe6, 0xcf, 0xe1, 0x9e, 0xa8, 0x2c, 0x63, 0x16, 0x01, 0x3f, 0x58, 0xe2, 0x89, 0xa9,
                                                      0x0d, 0x38, 0x34, 0x1b, 0xab, 0x33, 0xff, 0xb0, 0xbb, 0x48, 0x0c, 0x5f, 0xb9, 0xb1, 0xcd, 0x2e,
                                                      0xc5, 0xf3, 0xdb, 0x47, 0xe5, 0xa5, 0x9c, 0x77, 0x0a, 0xa6, 0x20, 0x68, 0xfe, 0x7f, 0xc1, 0xad
                                                  };

        internal RC2ManagedTransform(ISymmetricAlgorithm algorithm, byte[] rgbKey, byte[] rgbIv, TransformDirection transformDirection)
            : base(algorithm, rgbIv, transformDirection, Endianness.Big)
        {
            Mode = algorithm.ExtendedMode;
            ExpandKey(rgbKey);
        }

        internal bool IsWeakKey
        {
            get
            {
                return false;
            }
        }

        private void ExpandKey(byte[] key)
        {
            _keyBuffer = new byte[128];
            _keyWords = new ushort[64];
            key.CopyTo(_keyBuffer, 0);
            int t = key.Length;
            for (int i = t; i < 128; i++)
            {
                _keyBuffer[i] = _piTable[(byte)(_keyBuffer[i - 1] + _keyBuffer[i - t])];
            }
            _keyBuffer[128 - t] = _piTable[_keyBuffer[128 - t]];
            for (int i = 127 - t; i >= 0; i--)
            {
                _keyBuffer[i] = _piTable[_keyBuffer[i + 1] ^ _keyBuffer[i + t]];
            }
            int index = 0;
            for (int i = 0; i < 64; i++)
            {
                _keyWords[i] = (ushort)(_keyBuffer[index++] | (_keyBuffer[index++] << 8));
            }
        }

        /// <summary>
        /// Performs the encryption transformation on a block of bytes that
        /// have been translated into words using the big endian convention.
        /// </summary>
        /// <param name="plain">
        /// The words to encrypt.
        /// </param>
        [CLSCompliant(false)]
        protected internal override void Encrypt(uint[] plain)
        {
        }

        /// <summary>
        /// Performs the decryption transformation on a block of bytes that
        /// have been translated into words using the big endian convention.
        /// </summary>
        /// <param name="cipher">
        /// The words to decrypt.
        /// </param>
        [CLSCompliant(false)]
        protected internal override void Decrypt(uint[] cipher)
        {
        }

        /// <summary>
        /// Encrypts a single block of bytes, writing the result into the
        /// provided array.
        /// </summary>
        /// <param name="block">
        /// The block of bytes to be encrypted.
        /// </param>
        protected override void EncryptBlock(byte[] block)
        {
            ushort[] words = Utils.BytesTo16BitWordsLittleEndian(block);
            Encrypt(words);
            Utils.Write16BitWordsIntoBytesLittleEndian(words, block);
        }

        /// <summary>
        /// Decrypts a single block of bytes, writing the result into the
        /// provided array.
        /// </summary>
        /// <param name="block">
        /// The block of bytes to be decrypted.
        /// </param>
        protected override void DecryptBlock(byte[] block)
        {
            ushort[] words = Utils.BytesTo16BitWordsLittleEndian(block);
            Decrypt(words);
            Utils.Write16BitWordsIntoBytesLittleEndian(words, block);
        }

        private void Encrypt(ushort[] words)
        {
            int keyIndex = 0;
            for (int i = 0; i < 5; i++)
            {
                words[0] = (ushort)(words[0] + _keyWords[keyIndex++] + (words[3] & words[2]) + ((~words[3]) & words[1]));
                words[0] = (ushort)(words[0] << 1 | words[0] >> 15);
                words[1] = (ushort)(words[1] + _keyWords[keyIndex++] + (words[0] & words[3]) + ((~words[0]) & words[2]));
                words[1] = (ushort)(words[1] << 2 | words[1] >> 14);
                words[2] = (ushort)(words[2] + _keyWords[keyIndex++] + (words[1] & words[0]) + ((~words[1]) & words[3]));
                words[2] = (ushort)(words[2] << 3 | words[2] >> 13);
                words[3] = (ushort)(words[3] + _keyWords[keyIndex++] + (words[2] & words[1]) + ((~words[2]) & words[0]));
                words[3] = (ushort)(words[3] << 5 | words[3] >> 11);
            }
            words[0] = (ushort)(words[0] + _keyWords[words[3] & 63]);
            words[1] = (ushort)(words[1] + _keyWords[words[0] & 63]);
            words[2] = (ushort)(words[2] + _keyWords[words[1] & 63]);
            words[3] = (ushort)(words[3] + _keyWords[words[2] & 63]);
            for (int i = 0; i < 6; i++)
            {
                words[0] = (ushort)(words[0] + _keyWords[keyIndex++] + (words[3] & words[2]) + ((~words[3]) & words[1]));
                words[0] = (ushort)(words[0] << 1 | words[0] >> 15);
                words[1] = (ushort)(words[1] + _keyWords[keyIndex++] + (words[0] & words[3]) + ((~words[0]) & words[2]));
                words[1] = (ushort)(words[1] << 2 | words[1] >> 14);
                words[2] = (ushort)(words[2] + _keyWords[keyIndex++] + (words[1] & words[0]) + ((~words[1]) & words[3]));
                words[2] = (ushort)(words[2] << 3 | words[2] >> 13);
                words[3] = (ushort)(words[3] + _keyWords[keyIndex++] + (words[2] & words[1]) + ((~words[2]) & words[0]));
                words[3] = (ushort)(words[3] << 5 | words[3] >> 11);
            }
            words[0] = (ushort)(words[0] + _keyWords[words[3] & 63]);
            words[1] = (ushort)(words[1] + _keyWords[words[0] & 63]);
            words[2] = (ushort)(words[2] + _keyWords[words[1] & 63]);
            words[3] = (ushort)(words[3] + _keyWords[words[2] & 63]);
            for (int i = 0; i < 5; i++)
            {
                words[0] = (ushort)(words[0] + _keyWords[keyIndex++] + (words[3] & words[2]) + ((~words[3]) & words[1]));
                words[0] = (ushort)(words[0] << 1 | words[0] >> 15);
                words[1] = (ushort)(words[1] + _keyWords[keyIndex++] + (words[0] & words[3]) + ((~words[0]) & words[2]));
                words[1] = (ushort)(words[1] << 2 | words[1] >> 14);
                words[2] = (ushort)(words[2] + _keyWords[keyIndex++] + (words[1] & words[0]) + ((~words[1]) & words[3]));
                words[2] = (ushort)(words[2] << 3 | words[2] >> 13);
                words[3] = (ushort)(words[3] + _keyWords[keyIndex++] + (words[2] & words[1]) + ((~words[2]) & words[0]));
                words[3] = (ushort)(words[3] << 5 | words[3] >> 11);
            }
        }

        private void Decrypt(ushort[] words)
        {
            int keyIndex = 63;
            for (int i = 0; i < 5; i++)
            {
                words[3] = (ushort)(words[3] << 11 | words[3] >> 5);
                words[3] = (ushort)(words[3] - _keyWords[keyIndex--] - (words[2] & words[1]) - ((~words[2]) & words[0]));
                words[2] = (ushort)(words[2] << 13 | words[2] >> 3);
                words[2] = (ushort)(words[2] - _keyWords[keyIndex--] - (words[1] & words[0]) - ((~words[1]) & words[3]));
                words[1] = (ushort)(words[1] << 14 | words[1] >> 2);
                words[1] = (ushort)(words[1] - _keyWords[keyIndex--] - (words[0] & words[3]) - ((~words[0]) & words[2]));
                words[0] = (ushort)(words[0] << 15 | words[0] >> 1);
                words[0] = (ushort)(words[0] - _keyWords[keyIndex--] - (words[3] & words[2]) - ((~words[3]) & words[1]));
            }
            words[3] = (ushort)(words[3] - _keyWords[words[2] & 63]);
            words[2] = (ushort)(words[2] - _keyWords[words[1] & 63]);
            words[1] = (ushort)(words[1] - _keyWords[words[0] & 63]);
            words[0] = (ushort)(words[0] - _keyWords[words[3] & 63]);
            for (int i = 0; i < 6; i++)
            {
                words[3] = (ushort)(words[3] << 11 | words[3] >> 5);
                words[3] = (ushort)(words[3] - _keyWords[keyIndex--] - (words[2] & words[1]) - ((~words[2]) & words[0]));
                words[2] = (ushort)(words[2] << 13 | words[2] >> 3);
                words[2] = (ushort)(words[2] - _keyWords[keyIndex--] - (words[1] & words[0]) - ((~words[1]) & words[3]));
                words[1] = (ushort)(words[1] << 14 | words[1] >> 2);
                words[1] = (ushort)(words[1] - _keyWords[keyIndex--] - (words[0] & words[3]) - ((~words[0]) & words[2]));
                words[0] = (ushort)(words[0] << 15 | words[0] >> 1);
                words[0] = (ushort)(words[0] - _keyWords[keyIndex--] - (words[3] & words[2]) - ((~words[3]) & words[1]));
            }
            words[3] = (ushort)(words[3] - _keyWords[words[2] & 63]);
            words[2] = (ushort)(words[2] - _keyWords[words[1] & 63]);
            words[1] = (ushort)(words[1] - _keyWords[words[0] & 63]);
            words[0] = (ushort)(words[0] - _keyWords[words[3] & 63]);
            for (int i = 0; i < 5; i++)
            {
                words[3] = (ushort)(words[3] << 11 | words[3] >> 5);
                words[3] = (ushort)(words[3] - _keyWords[keyIndex--] - (words[2] & words[1]) - ((~words[2]) & words[0]));
                words[2] = (ushort)(words[2] << 13 | words[2] >> 3);
                words[2] = (ushort)(words[2] - _keyWords[keyIndex--] - (words[1] & words[0]) - ((~words[1]) & words[3]));
                words[1] = (ushort)(words[1] << 14 | words[1] >> 2);
                words[1] = (ushort)(words[1] - _keyWords[keyIndex--] - (words[0] & words[3]) - ((~words[0]) & words[2]));
                words[0] = (ushort)(words[0] << 15 | words[0] >> 1);
                words[0] = (ushort)(words[0] - _keyWords[keyIndex--] - (words[3] & words[2]) - ((~words[3]) & words[1]));
            }
        }

        /// <summary>
        /// Clears all potentially sensitive data stores.
        /// </summary>
        protected internal override void Reset()
        {
            if (_keyBuffer != null)
            {
                Array.Clear(_keyBuffer, 0, _keyBuffer.Length);
            }
            if (_keyWords != null)
            {
                Array.Clear(_keyWords, 0, _keyWords.Length);
            }
            base.Reset();
        }
    }
}